1. Field of the Invention
The present invention relates to an automatic lane following control system and method for vehicles, and more particularly to an automatic lane following control system and method for vehicles by considering a roll angle of a vehicle and a bank angle of a vehicle lane.
2. Description of Related Art
Statistics from the Ministry of Transportation show that vehicle accidents caused by lane deviation are about 51% in all collisions. In another report from the US Interstate Highway and Transportation Association, death rate caused by the vehicle lane deviation is about 58% in all traffic accident mortality. Accordingly, the probability of collision accident resulted from vehicles deviation is very high, and the vehicle lane deviation is easy to cause the death.
Therefore, car manufacturers design a lane following control (LFC) system. A center control system of the LFC system obtains a lane geometry data relative to the vehicle via a sensing system and maintains the vehicle on a centerline of a vehicle lane by controlling a steering system so as to prevent the vehicle from deviating from the vehicle lane to avoid the occurrence of traffic accidents and reduce the driving liability for a driver.
Most of the conventional LFC systems use image sensors to detect lane lines. When the vehicle is driving on a flat road, the LFC system can successfully control a steering wheel of the vehicle and allow the vehicle to travel between two lane lines.
However, when a roll angle is generated in the vehicle or a bank angle exists in the vehicle lane, the LFC system may not control the steering wheel well. Therefore, the vehicle may not efficiently keep driving between the two lane lines.
In Chinese Patent No. CN101778753B, a method and system for keeping vehicle in a lane is disclosed and prevents the vehicle from deviating from the lane when driving through a curve road. By comparing a future trajectory of the vehicle with an expecting position of the lane, the steering of the wheel is determined. However, the patent does not consider a roll angle of the vehicle, and the operating method may not be able to keep the vehicle between lane lines.
Accordingly, with reference to FIG. 6, it is necessary to consider a situation in which a vehicle 60 with a roll angle 61 or a bank angle existing in the vehicle lane to improve the conventional LFC system. Therefore, the LFC system will not deviate too much from the land and the vehicle is kept driving between the two lane lines so as to reduce a risk of accidental injury due to fatigue or deviation from the vehicle lane.